ADOPTED 2018 WATER AND SEWER PLAN CHAPTER 3 WATER PLAN FOR COMMUNITY SYSTEMS Drinking water is supplied to Prince George’s County primarily through community water supply facilities such as the Washington Suburban Sanitary Commission (WSSC). In rural areas water is provided through individual wells. This chapter discusses the sources of drinking water, identifies major treatment and transmission providers, provides an inventory of community system wells, and addresses water demand and production issues. It also outlines key regional water supply agreements. 3.1 RESOURCES The Patuxent and Potomac rivers provide the major source of the County’s surface (or raw) water supply. The Potomac River is the larger of the two sources of raw water, supplying more than 40 billion gallons of water annually to the bicounty area of Montgomery and Prince George’s counties. In addition to water from the free-flowing river, there are three impounded (or storage) areas that can supplement flows into the Potomac River during periods of low flow. The Jennings Randolph Reservoir is located near Bloomington, Maryland, on the North Branch of the Potomac River at the State boundary with West Virginia, 200 miles upstream from the Potomac intake at Watkins Island. This reservoir was completed in 1981 and provides 30 billion gallons of water storage with 13 billion gallons currently allocated to water supply. The remaining capacity is used for both water quality purposes to help buffer acidity downstream resulting from acid mine drainage, and recreation. The Savage Reservoir is located on the Savage River, slightly north of the Potomac River and the Jennings Randolph Reservoir. The Savage River flows into the Potomac just downstream of the Jennings Randolph Reservoir. It is owned by the Upper Potomac River Commission and supplements the Jennings Randolph supply augmentations to provide adequate water supply to downstream users including WSSC for Prince George’s County, and meets water quality standards in the Potomac River. The Savage Reservoir has a gross capacity of 10.4 billion gallons, and the capacity of the reservoir used for water supply is 6.3 billion gallons. The U.S. Army Corps of Engineers are responsible for the maintenance and operation of the Jennings Randolph and Savage dams. Little Seneca Lake was built solely for water supply and is located near Boyds, Maryland. It has a gross capacity of 3.9 billion gallons. WSSC owns and operates the Little Seneca Dam and controls water releases from the facility. Table 3-1 provides an inventory of existing storage facilities (impounded water supply) on the Potomac River. The Patuxent River is located along the northeastern border between Montgomery and Howard counties, and is the second major source of raw water which is supplied and treated by WSSC to the two counties. There are two water supply impoundments along the Patuxent River operated by the WSSC – the Triadelphia and the T.H. Duckett Reservoirs, created by the Brighton and T. Howard Duckett dams, respectively. They are used solely for water supply. The Triadelphia Reservoir is located at Brighton Dam in Montgomery County, 14 miles north of the Chapter 3, Water Plan For Community Systems 3- 1 ADOPTED 2018 WATER AND SEWER PLAN Table 3-1 Inventory of Existing Storage Facilities Potomac River – Jennings Randolph and Little Seneca Lake JENNINGS LITTLE SENECA RANDOLPH Crest Elevation (above sea level) 1,514 Feet 408 Feet Spillway Length 210 Feet Flooded Area at Crest Elevation 1,247 Acres 530 Acres Area of Land Owned by WSSC None 530 Acres First Overflow of Dam Crest N/A 1985 Total Length of Dam 2,130 Feet 600 Feet Capacity of Reservoir Used For Water Supply 13 Billion Gals. 3.9 Billion Gals. Safe Yield 155 mgd Average Withdrawal* Maximum Historical Withdrawal* 290 mgd 275 mgd *1999 was the first time these sources were tapped to relieve drought conditions. northernmost tip of Washington, D.C., and has a gross storage capacity of 6.4 billion gallons. The T.H. Duckett Reservoir is located about two miles northwest of Laurel, in Prince George’s County, and has a gross storage capacity of 5.7 billion gallons. Table 3-2 provides an inventory of existing storage facilities (impounded water supply) on the Patuxent River. Table 3-2 Inventory of Existing Storage Facilities Patuxent River -- WSSC Reservoirs TRIADELPHIA T.H. DUCKETT Crest Elevation (above sea level) 366.4 Feet 286.4 Feet Spillway Length 234 Feet 189 Feet Total Length of Dam 995 Feet 840 Feet Height of Crest above Stream Bed 64 Feet 125.45 Feet Flooded Area of Crest Elevation 800 Acres 815 Acres Area of Land Owned 2,936 Acres 3,023 Acres Water Overflowed Crest for 1st Time 1944 August 1955 Gross Capacity of Reservoir 6.4 Billion Gallons 5.7 Billion Gallons Capacity for Water Supply 5.6 Billion Gallons 5.0 Billion Gallons Safe Yield (mgd) 45.3 mgd – Combined Average Daily Withdrawal (mgd) 50.6 mgd – Combined Maximum Daily Withdrawal (mgd) 72 mgd – Combined Chapter 3, Water Plan For Community Systems 3- 2 ADOPTED 2018 WATER AND SEWER PLAN 3.2 TREATMENT AND TRANSMISSION The largest agencies involved in supplying water to Prince George's County are WSSC, the City of Bowie, and the Beltsville Agricultural Research Center. WSSC supplies water to Prince George's and Montgomery counties from the Potomac and Patuxent rivers through two water filtration plants (WFP), Potomac WTP and Patuxent WTP. The WSSC Water Network, found as Appendix 3-1 of this chapter, demonstrates flexibility to provide Prince George’s County with water from both sources and WFPs. 3.2.1 Potomac Water Treatment Plant WSSC withdraws water from the Potomac River near Watts Branch for processing at the Potomac Water Treatment Plant. The Potomac Plant is the subject of ongoing planning and construction to maintain treatment capacity while meeting new water quality regulations. The Potomac Plant has a State-permitted maximum intake capacity of 300 million gallons per day (mgd) and a treatment capacity of 288 mgd. The Potomac Plant is the subject of an ongoing planning effort to maintain treatment capacity while meeting new water quality regulations that may require modifications to current treatment processes. The present average output capacity, which is water that can be reliably delivered from the Plant through the Potomac pumping station, is 337 mgd. The Potomac Plant is also the subject of a Source Water Assessment (SWA) study required by the Safe Drinking Water Act. The study is funded by the Maryland Department of the Environment (MDE) and is intended to assess the raw water upstream of the Potomac Plant’s intake for any possible sources of contamination relevant to water supply, as well as the susceptibility of the plant to the contaminants. The Potomac Plant currently has solid removal processes which include provisions for separating filter backwash and for pumping, thickening, dewatering and disposing of sedimentation solids. In April 2016, a consent decree was entered by the U.S. District Court of Maryland. Under the terms of the consent decree, WSSC is required to undertake short-term operational changes and capital improvements at the Plant to reduce significantly the amount of solids being discharged into the river, and must plan, design, and implement long-term upgrades to achieve the effluent limits, conditions, and waste load allocations established by the Maryland Department of the Environment to be incorporated into a new discharge permit to be issued by the State. Finished water from the Potomac Plant which serves Prince Georges County is first pumped into the Montgomery Main Zone and then into the Prince George's Main Zone through by means of the Bi-County Tunnel and pressure reduction valves. From the Prince George's Main Zone, water is transmitted to the Prince George's High Zone through the Central Avenue and Hill Road pumping stations. Water moves from the High Zone to the Prince George's Intermediate Zone by way of pressure reduction valves or pumping at the Central Avenue Pumping Station. The Clinton and Potomac zones are fed from the High Zone through pressure reduction valves. Finally, the Marlboro Zone is fed by pressure reduction from the Prince George's Intermediate Zone. Chapter 3, Water Plan For Community Systems 3- 3 ADOPTED 2018 WATER AND SEWER PLAN The water transmission network is shown on the map The Water Network, included as Appendix 3-1. An important facility for Prince Georges County that conveys finished water from the Potomac Plant in Montgomery County into Prince George's County is the Bi-County tunnel, also known as Project 80 which became operational in 2015. 3.2.2 Patuxent Water Treatment Plant The Triadelphia and the Duckett reservoirs provide the raw water source for the Patuxent Water Treatment Plant. To protect these reservoirs against water quality degradation and against excessive capacity loss due to sedimentation, the Patuxent Reservoirs Watershed Protection Agreement was signed in 1996 between seven local governments and agencies with interest in the issue. Included in the Agreement are Prince George’s County and the WSSC. The Agreement has created a policy board composed of the executive-level representatives of the seven agencies. They meet once a year and supervise the work conducted or proposed by a Technical Advisory Committee (TAC). The TAC is engaged in monitoring, modeling, and field assessments for the reservoirs and its watershed. It also provides support to the SWA being conducted by MDE. The Patuxent Water Treatment Plant can currently treat a nominal capacity of 56 mgd, and emergency capacity of 72 mgd. However, the raw water pump station can supply a maximum of 68.5 mgd to the plant. Phase II of the Patuxent Treatment Plant expansion, is currently under construction and will allow for 72 mgd nominal capacity and 110 mgd emergency capacity.